This application relates generally to communications networks, and more particularly, to detecting faults in communication lines.
Recently, there has been an increased demand for the subscriber lines of plain old telephone services (POTS""s) to carry high-speed digital signals. The demand has been stimulated by home access to both the Internet and distant office computers. Both types of access typically employ a POTS line as part of the path for carrying digital signals.
POTS""s lines were built to carry voice signals at audible frequencies and can also carry digital signals as tone signals in the near audible frequency range. Modern digital services such as ISDN and ADSL transmit data at frequencies well above the audible range. At these higher frequencies, POTS""s lines that transmit voice signals well may transmit digital signals poorly. Nevertheless, many telephone operating companies (TELCO""s) would like to offer ISDN and/or ADSL data services to their subscribers.
Telephone lines between a TELCO switch and subscribers"" premises are frequent sources of poor performance at the high frequencies characteristic of ISDN and ADSL transmissions. Nevertheless, high cost has made widespread replacement of these subscriber lines an undesirable solution for providing subscribers with lines capable of supporting ISDN and ADSL. A less expensive alternative would be to repair or remove only those subscriber lines that are inadequate for transmitting high-speed digital data.
To limit replacement or repair to inadequate lines, TELCO""s have placed some emphasis on developing methods for predicting which subscriber lines will support data services, such as ISDN and ADSL. Some emphasis has been also placed on predicting frequency ranges at which such data services will be supported. Some methods have also been developed for finding faults in subscriber lines already supporting data services so that such faults can be repaired.
Current methods for predicting the ability of subscriber lines to support high-speed digital transmissions are typically not automated, labor intensive, and entail test access at multiple points. Often, these methods entail using skilled interpretations of high frequency measurements of line parameters to determine data transmission abilities. At a network scale, such tests are very expensive to implement.
The present invention is directed to overcoming or, at least, reducing the affects of one or more of the problems set forth above.
In a first aspect, the invention provides a method of testing a subscriber line. The method includes providing a classifier to predict a performance characteristic of the line based at least in part on a value of an auxiliary variable. Each value of the auxiliary variable represents a property of the line. The method also includes performing electrical measurements on the subscriber line, using the measurements to predict a value of the auxiliary variable, and predicting the performance characteristic of the line. The act of predicting the characteristic applies the classifier to the predicted value of auxiliary variable.
In a second aspect, the invention provides a method of detecting a condition or fault in a subscriber line. The method includes classifying the line as a nominal line or a non-nominal line from electrical measurements. The method determines whether the line has the condition or fault from the electrical measurements and the classification.
In a third aspect, the invention provides a method for detecting a fault in a subscriber line. The method includes making a preliminary classification of the line as qualified or disqualified for a data service line in response to electrical measurements thereon. The method also includes determining whether the line has a fault from the electrical measurements and the preliminary classification.
In a fourth aspect, the invention provides a method of detecting a fault in a subscriber line. The method includes making a preliminary classification of the line as qualified or disqualified for a data service line in response to electrical measurements thereon. The method also includes determining whether the line has a fault from the electrical measurements and the preliminary classification.
In a fifth aspect, the invention provides a method of creating a stack of classifiers for detecting line faults. The method includes selecting a learning set of subscriber lines and determining the form of the classifier from values of features and auxiliary variables of the lines. A portion of the lines have the fault, and a portion of the lines do not have the fault. The value of the auxiliary variable determines whether the associated line is one of nominal and qualified for a data service.
In a sixth aspect, the invention provides a program storage device storing a computer executable program of instructions for performing one or more of the above-described methods.
Various embodiments use test accesses, which provide data on low frequency electrical properties of subscriber lines, to make predictions about high frequency performance.